Water glass is a material extensively used in industry. It is a colorless, highly viscous liquid material that is usually available as a thick aqueous solution of an alkali silicate produced by fusing silicon dioxide and an alkali together. Upon standing in the atmosphere, water glass solidifies as a result of water evaporation. Because of this property, water glass is extensively used in the production of artificial stones, ceramics and adhesives for corrugated board.
However, upon contact with water, the solidified water glass absorbs water and returns to a viscous liquid form. Therefore, water glass cannot be incorporated in articles that are used outdoors under humid conditions or in areas where they are put into direct contact with water. Therefore, one great disadvantage of water glass is its low resistance to water. Furthermore, if solidified water glass is heated at a temperature of higher than 150.degree. C., its strength is reduced to such an extent that it is no longer usable in shaped articles or adhesives.
It is known that upon addition of Ca, Mg, Al, Ba or the like, water glass solidifies and becomes water-insoluble or resistant to water. However, if these elements are added in an ionic form, the water glass gels so quickly that it does not permit practical operations such as shaping or coating. It is also known that the solidification of water glass may be accelerated by the addition of a hydrous magnesium silicate mineral such as sepiolite. However, the water glass composition solidified by this method does not provide satisfactory hot water-resistance.